Chapter+3

=toc Section 1=

- In a car accident you can protect yourself from getting a very serious injury by wearing your seatbelt and making sure all airbags in a car work well. On a bicycle, it is important to wear a helmet and even elbow/knee pads.
 * What Do You Think:**

1. 2. Novice Analyst; I wasn't very surprised because the questions asked in the test weren't common knowledge. 3.
 * Investigate:**

(yes/no) || New Cars (1,2,3) || and forward || no || 1 ||
 * ** Safety features ** || Means of protection || Pre-1960 cars
 * seat belt || Keep body from moving with car || no || 1 ||
 * head restraints || Allow the back of the seat&headrest to move back
 * front airbags || Prevent injuries during car crashes || no || 1 ||
 * back up sensing system || To be able to see blind spots behind you || no || 3 ||
 * front crumple zones || To redirect shock and absorb shock || no || 2 ||
 * rear crumple zones || To redirect and absorb shock || no || 2 ||
 * side-impact beams in doors || Deflect the force of a side-impact collision || no || 2 ||
 * shoulder belts for all seats || Prevent movement with car || no || 1 ||
 * anti-lock braking systems (ABS) || Prevent skidding on road || no || 1 ||
 * tempered shatterproof glass || Help prevent cuts during a crash || yes || 1 ||
 * side airbags || Keep safety during crash on all sides || no || 2 ||
 * turn signals || Show surrounding people/cars what you are doing || yes || 1 ||
 * electronic stability control || Help resist rollovers || no || 2/3 ||
 * energy-absorbing collapsible steering column || Prevents chest trauma || no || 1 ||

- In Crest Hill four close friends were killed as their car left the road, flipped over and hit a tree around 50 feet from the pavement probably due to speeding. If they were going slower they would have not lost as much control of the car and could have spared their lives. http://archive.chicagobreakingnews.com/2010/01/cops-four-dead-in-car-accident-in-crest-hill.html
 * Car Crash Summary:**

- Four wheel drive crashes are due to: growing number of kilometers travel and the tendency to increase speed under the impression that safety features will protect - If you are in an accident in a safer vehicle, the chances of injury are limited.
 * Physics Talk Summary:**

1. Three ways that car safety has improved since the 1960s are side airbags, head restraints and shoulder belts. 2. Two explanations for 4WD accidents are because of the growing number of kilometers travled and the tendency to increase speed under the impression that safety features will protect.
 * Checking Up:**

1. Side Airbags **S**, Front Airbags **F**, Back Up Sensing System **R**, Crash Resistant Door Pillars **S**, Front Crumple Zone **F**, Rear Crumple Zone **R**, Impact Absorbing Dashboard **F**, Impact Absorbing Armrests **S**, Traction Control **T** 2. Helmet, shoulder pads, knee pads and sneakers. 3. Helmet, shoulder pads, high socks, knee pads, wrist pads 4. Helmet, shoulder pads, knee pads, pants and sneakers.
 * Physics To Go:**

- To protect oneself from serious injury in an accident you need to wear your seatbelt and make sure all safety precautions in the car are working effectively. If not in a car, one needs to wear all the protective gear recommended to save from any broken bones or bad bruising.
 * What Do You Think Now:**

=Section 2=


 * What Do You Think:**


 * Investigate:**
 * __Objectives:__ **


 * What happens to a passenger involved in a car accident without and with a seatbelt?
 * What factors affect the passenger’s safety after a collision?
 * How would a seat belt for a race car be different from one available on a regular car?

__Hypothesis:__ A passenger involved in a car accident without a seatbelt is more likely to get thrown out of the car/through the windshield and get more hurt. With a seatbelt on, a passenger might end up a little damaged but much more safe and secure in the car. After a collision the factors that affect the passenger's safety are how damaged the car is and if the passenger can get out of the car. A seatbelt for a race car is much more safe and has many different straps. In a regular car the seatbelt is just across the chest and across your waist.

__Materials:__ - Clay Person - Ramp - Textbooks - Ribbons - Meterstick

__Procedure:__ 1. Make a clay figure and then place the figure in the cart. 2. Arrange a ramp so that the endstop is at the bottom of the ramp. 3. Adjust the height of the ramp to make a very shallow incline. 4. Send the cart down the ramp. 5. Very gradually increase the height of the ramp until significant “injury” happens to your figure. Make a note of this height. 6. Fix your clay figure. Create a seatbelt for the figure and take a "Before" picture and post in your data table. 7. Send your cart and passenger down the ramp at the same height as in Step 5. Be sure to record your observations specifically and carefully. Take an "After" picture and post in your data table to supplement your written observations. 8. Repeat Steps 6 and 7, using different types of material for the seatbelt.

__Data and observations:__ Injury Height with no seatbelt: .163 m is so small so it puts too much pressure in small area which digs into his body. ||  ||   || as a result of the narrow wire. When the cart plunged forward, he moved forward as well, pushing against his wire restraint. We observed lacerations to his shoulder and legs. ||  || the slant, he was in good condition and the ribbon was a decently sturdy seatbelt. After released down the slant the seatbelt restricted the person from falling out of the car. The damage wasn't very severe, he might have went through the windshield. Only a broken arm and maybe some injuries on the back/neck. Overall the seatbelt protected the clay person from death but no serious injuries. || 2- Courtney and Ross ||
 * **//Type of Seatbelt//** || //**Before Picture**// || //**After Picture**// || //**Description and Observations**// || //**Group**// ||
 * Thread || [[image:1st_dskfj.jpg width="192" height="144"]] || [[image:dsjhfl.jpg width="192" height="144"]] ||  || The seatbelt holds him but the thread
 * Wire || [[image:first_hdjsk.jpg width="192" height="144"]] || [[image:second_hj.jpg width="192" height="144"]] || The clay passenger suffered cuts
 * String ||  ||   ||   ||   ||
 * Yarn || [[image:hello_1.jpg width="192" height="144"]] || [[image:hello2.jpg width="192" height="144"]] || The little clay man was sent flying down the incline with a two-point seatbelt made of yarn around his waist and across his body and shoudler, and crashed into the end, without significant injury. No cuts could be seen from the force of the yarn on the man and no body parts were missing or out of place. The cart hit the end of the track and the little clay man did not move sitting in place where I had placed him on the cart. ||  ||
 * Ribbon || [[image:before.png width="152" height="166"]] || [[image:after.png width="224" height="137"]] || Before we let our clay person go down
 * 1-in masking ||  ||   ||   ||   ||

__Questions:__ - Inertia: - Force: - Pressure: - The passenger's body is thrown forward and then backwards when the car stops abruptly. - The neck and the arms were in the greatest damage. - The passenger in the car stays in place until an unbalanced force (stopping abruptly or in a crash) forces the passenger to be thrown forward or backwards in the car. - Thick and strong materials that cover more parts of your bodies. They work better because it's more force against you to keep you in your seat. - First Collision: The automobile strikes an object (pole/wall etc), the object exerts the force that brings the automobile to rest. - Second Collision: When the automobile stops, the body keeps moving. The structure of the automobile exerts the froce that brings the body to rest. - Third Collision: The body stops, but the heart, the brain, and other organs keep moving. The body wall exerts the force that brings the organs to rest.
 * 1. Define the terms: inertia, force and pressure.**
 * 2. In the collision, the car stops abruptly. What happens to the “passenger”?**
 * 3. What parts of your passenger were in greatest danger (most damaged)?**
 * 4. What does Newton’s first law have to do with this?**
 * 5. What materials were most effective as seatbelts? Why?**
 * 6. Use Newton's first law of motion to describe the three collisions.**
 * 7. Why does a broad band of material work better as a seatbelt than a narrow wire?**
 * -** It is stronger and covers more of the body than a narrow wire. Plus it is more comfortable on the body.

__Conclusion:__ - The seatbelt restricts the passengers of a car so when the car gets into a crash the passenger stays in their seat and stays safe. The thickness of the belt and the areas of the body that the belt cover affect the effectiveness of a seatbelt. When designing a seatbelt for a race car you need to consider how fast the car is going and how sharp the turns that the car is making. Experimental error can come from not testing our seatbelt more than once, which would result in not knowing how it definitely worked. - I would repeat the experiment 3 times and have each person use the same amount of books so our results all come form the same incline of the ramp.
 * 1. Using Newton's First law of Motion, explain why a seat belt is an important safety feature in a vehicle. What factors affect the effectiveness of a seatbelt? What would you need to consider when designing a seatbelt for a race car? Use specific observations from this investigation to support your answers to these questions.**
 * 2. Explain at least 1 cause of experimental error. Be sure you describe a specific reason.**
 * 3. How would you improve the results of this lab? (In other words, what would you change about the materials or procedure to eliminate or reduce the experimental error you describe above?)**

=Section 3=


 * Objective:**
 * How does an air bag protect you during an accident?


 * Hypothesis:** An airbag protects you during an accident by applying a force against your motion to stop you from slamming into the car/through the window during a crash.

- Egg - Bowl of flour - Ruler / meter stick - Plastic Bag
 * Materials:**

// 1. Measure the length of your egg #1. Measure the mass of your egg. Record this information. // // 2. Place an egg in a ziplock bag, squeezing out all of the air in the bag before sealing. // // 3. Hold a ruler up on the table vertically. Hold the egg vertically at the 2 cm mark. (Keep the excess bag on top.) Drop it. Record your observations. // // 4. Hold the egg the same exact way at the 4-cm mark and repeat. Continue this process until the egg shell is slightly cracked. // // 5. Continue until the egg is smashed and the yolk leaks out. Measure the amount of egg still undamaged. How much of the egg is smashed? Be sure to record detailed observations. // // 6. Fill a bowl with flour and place the bowl inside of the box lid. // // 7. Measure the length of your egg #2. Measure the mass of your egg. Record this information. // // 8. Drop the egg from the smash height (Step 5). Measure the amount of egg sticking up out of the rice bed. How much of the egg is buried in the rice? Also, record your observations. // // 9. Repeat this, increasing the height in 2-cm increments until the egg is cracked, and then smashed. //
 * Procedure:**

//**Data and observations:**// __First Egg:__ The egg weighed .058 kg and is 5 1/2 cm high. 1 1/2 cm were damaged __Second Egg:__ The egg weighed .057 kg and is 5 cm high.
 * **Egg #** || **Drop Height** || **Cracked or Smashed?** || **Description and Observations** || **GPE** (J) || **Work** (J) || **Force** (N) ||
 * 1 || 2 cm || Really slight crack || Heard the crack, very little and thin. || .01 || .01 ||  ||
 * || 4 cm || Slight crack || Same crack expanded and bottom is cracked in a star shape || .02 || .02 ||  ||
 * || 6 cm || Crack and dented || Bottom is dented in and the crack has expanded again || .03 || .03 ||  ||
 * || 8 cm || Crack / dented || Both slightly increased || .04 || .04 ||  ||
 * || 10 cm || Crack / dented || See into the bottom of the egg, crack is getting longer || .05 || .05 ||  ||
 * || 12 cm || Cracked and dented || Yolk is beginning to come out, crack is very intense || .06 || .06 ||  ||
 * || 14 cm || CRACKED! || Yolk is really coming out, the whole bottom is cracked || .07 || .07 ||  ||
 * || 16 cm || Really cracked || Whole bottom is flat, many cracks, more yolk || .08 || .08 ||  ||
 * || 18 cm || Slightly Smashed || Sides are opening || .09 || .09 ||  ||
 * || 20 cm || Almost smashed || One more side until fully smashed || .10 || .10 ||  ||
 * || 22 cm || SMASHED! || Yolk has left the egg || .11 || .11 ||  ||
 * 2 || 22 cm || none || Dent in flour: 1 cm || .122 || .122 || 12.2 ||
 * || 32 cm || none || Dent in flour: 1 1/2 cm || .179 || .179 || 11.9 ||
 * || 42 cm || none || Dent in flour: 1.8 cm || .234 || .234 || 13 ||
 * || 52 cm || none || Dent in flour: 2 cm || .290 || .290 || 14.5 ||
 * || 62 cm || none || Dent in flour: 2 1/2 cm || .346 || .346 || 13.84 ||
 * || 72 cm || none || Dent in flour: 3 cm || .402 || .402 || 13.4 ||
 * || 82 cm || none || Dent in flour: 3 cm || .458 || .458 || 15.3 ||
 * || 92 cm || none || Dent in flour: 3 cm || .513 || .513 || 17.1 ||
 * || 102 cm || none || Dent in flour: 3 cm || .569 || .569 || 18.6 ||
 * Calculations:** Show equation(s), numbers plugged in, and answer with correct units. Add columns in your data table to include these results.
 * What is the gravitational potential energy in each trial?
 * GPE = mgh
 * GPE = .058(9.8)(.02)
 * GPE = .01
 * How much work is done in each trial?
 * W = GPE
 * W = mgh
 * W = (.058)(9.8)(.02)
 * W = .01
 * How much force was used to stop the egg in each case of steps 5, 8 and 9?
 * W = Fd
 * .122 = F(.01)
 * F = 12.2
 * F = 12.2

1. This investigate is an analogy for a person in an automobile collision. What does the egg represent? What does the table represent? What does the flour represent? 2. Define the terms: Kinetic Energy and Work. 3. What factors determine an object's kinetic energy? 4. When work is done on an object, what is the effect on the object's kinetic energy? 5. How does the force needed to stop a moving object depend on the distance the force acts? 6. What difference does a soft landing area make on a passenger during a collision? 7. How does a cushion reduce the force needed to stop a passenger? 8. What does the law of conservation of energy have to do with this?
 * Questions:**
 * The egg represents the person, the flour represents the air bag and the table represents the damage on the person from different heights.**
 * Kinetic Energy:** energy an object possesses by the virtue of being in motion
 * Work:**
 * The mass of the object, and the speed of the object.**
 * The kinetic energy is equal to the work done on the object.**
 * The distance increases as the force decreases.**
 * It will cause the passenger less danger because the crash isn't going to be as dramatic.**
 * The cushion gives you a force to push you back into your seat instead of moving through the car.**
 * The law of conservation applies with the air bags acting against your body.**

- Using the law of conservation of energy, explain how an air bag can protect you during an accident. Use specific observations from this investigation to support your answers to these questions. - Explain at least 1 cause of experimental error. Be sure you describe a specific reason. - How would you improve the results of this lab? (In other words, what would you change about the materials or procedure to eliminate or reduce the experimental error you describe above?)
 * Conclusion:**
 * While your energy is moving forward the air bag expands against you and then as it deflates which allows you to move forward slowly.**
 * The experimental error can come from measuring the height from which we drop the egg from.**
 * I believe that flour was not a good choice to use because even when we dropped the egg from over 100 cm, the egg did not break. We needed a different substance to better represent an airbag.**

=Section 5=

1) The momentum on the stopped vehicle will be greater because the vehicle has a larger velocity. The stopped car acquired the same speed that the moving car had. 4) They prefer the heavier linemen because the will affect other teams players more because their mass is larger. The linemen need more momentum because the players going against them will be less weight but have faster speed. 5) The vehicle with the larger momentum. 6) p = mv 1000(10) = 10000 -- 10000 = 10000v The vehicle would have to go 1 m/s.
 * Physics To Go**:

=Section 6=

Objective: What physics principles do the traffic-accident investigators use to "reconstruct" the accident?

Materials: Two carts Motion detector Track

Procedure:


 * 1) Place a motion detector at the right end of a track. Open up data studio. Dump "Velocity" into "Graph" display, and enlarge this.
 * 2) <span style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0.5em; padding-bottom: 0px; padding-left: 3em; padding-right: 0px; padding-top: 0px;">Place a cart on the middle of the track with the velcro to the right. Call this the "target cart." Place a second identical cart on the right end of the track. Call this the "Bullet cart".
 * 3) <span style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0.5em; padding-bottom: 0px; padding-left: 3em; padding-right: 0px; padding-top: 0px;">Click "Start" on Data Studio, and then push the bullet cart very gently towards the target cart so that they collide and stick together. You may need to practice this a few times. Be sure to get your body out of the way of the motion detector!
 * 4) <span style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0.5em; padding-bottom: 0px; padding-left: 3em; padding-right: 0px; padding-top: 0px;">Examine the graph produced by the motion detector. Using the Smart Tool, find the velocity right before and right after the collision. Record this in your data table.
 * 5) <span style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0.5em; padding-bottom: 0px; padding-left: 3em; padding-right: 0px; padding-top: 0px;">Vary the masses of the carts and repeat the process 5 times.

//**Data and observations:**//
 * **Mass of Bullet Cart (kg)** || **Mass of Target Cart (kg)** || **Speed of Bullet Cart****(m/s)** || **Speed of Target cart (m/s)** || **Combined masses (kg)** || **Final Velocity of both carts (m/s)** || **Initial Momentum (kgm/s)** || **Final Momentum (kgm/s)** ||
 * .256 || .257 || .65 || 0 || .513 || .36 || .1664 || .1846 ||
 * .756 || .257 || .69 || 0 || 1.013 || .34 || .5216 || .3444 ||
 * .256 || .757 || .59 || 0 || 1.013 || .19 || .1510 || .1924 ||
 * 1.256 || .257 || 1.49 || 0 || 1.513 || .69 || 1.871 || 1.043 ||
 * .256 || 1.257 || .73 || 0 || 1.513 || .22 || .1868 || .3328 ||


 * Calculations:** Show equation(s), numbers plugged in, and answer with correct units. Add columns in your data table to include these results.
 * 1) <span style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0.5em; padding-bottom: 0px; padding-left: 3em; padding-right: 0px; padding-top: 0px;">Find the initial momentum of the bullet cart for each trial.
 * 2) <span style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0.5em; padding-bottom: 0px; padding-left: 3em; padding-right: 0px; padding-top: 0px;">p = mv
 * 3) <span style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0.5em; padding-bottom: 0px; padding-left: 3em; padding-right: 0px; padding-top: 0px;">p = .256(.65)
 * 4) <span style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0.5em; padding-bottom: 0px; padding-left: 3em; padding-right: 0px; padding-top: 0px;">p = .1664
 * 5) <span style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0.5em; padding-bottom: 0px; padding-left: 3em; padding-right: 0px; padding-top: 0px;">Find the initial momentum of the target cart for each trial.
 * 6) <span style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0.5em; padding-bottom: 0px; padding-left: 3em; padding-right: 0px; padding-top: 0px;">p = mv
 * 7) <span style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0.5em; padding-bottom: 0px; padding-left: 3em; padding-right: 0px; padding-top: 0px;">p = .257(0)
 * 8) <span style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0.5em; padding-bottom: 0px; padding-left: 3em; padding-right: 0px; padding-top: 0px;">p = 0
 * 9) <span style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0.5em; padding-bottom: 0px; padding-left: 3em; padding-right: 0px; padding-top: 0px;">Find the sum of the initial momenta of the two carts for each trial.
 * 10) <span style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0.5em; padding-bottom: 0px; padding-left: 3em; padding-right: 0px; padding-top: 0px;">0 + .1664 = .1664
 * 11) <span style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0.5em; padding-bottom: 0px; padding-left: 3em; padding-right: 0px; padding-top: 0px;">Find the final momentum of the combined carts for each trial.
 * 12) <span style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0.5em; padding-bottom: 0px; padding-left: 3em; padding-right: 0px; padding-top: 0px;">p = mv
 * 13) <span style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0.5em; padding-bottom: 0px; padding-left: 3em; padding-right: 0px; padding-top: 0px;">p = .513(.36)
 * 14) <span style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0.5em; padding-bottom: 0px; padding-left: 3em; padding-right: 0px; padding-top: 0px;">p = .1846

** *Read the Physics Talk p312 - 315 before answering the following questions. * ** 1. Compare the initial momenta (calc 3) to the final momentum (calc 4). (Allow for minor variations due to uncertainties of measurement.) 2. List the 6 types of collisions (top of page 312) and a brief description. 3. Which types of collisions are definitely inelastic? How do you know? 4. Which types of collisions are definitely elastic? How do you know? 5. Define the law of conservation of momentum. 6. Use the law of conservation of momentum to describe what happens when a cue ball hits the 15 balls in the middle of the pool table.
 * Questions:**
 * The final momentum is just a little higher than the initial momentum.**
 * Collision 1: one moving object hits a stationary object & both stick together and move off at the same speed**
 * Collision 2: two stationary objects explode by the release of a spring between them & move off in opposite directions**
 * Collision 3: one moving object hits a stationary object; the first object stops & the second object moves off**
 * Collision 4: one moving object hits a stationary object & both move off at different speeds**
 * Collision 5: two moving objects collide, and both objects move at different speeds after the collision**
 * Collision 6: two moving objects collide, and both objects stick together and move off at the same speed.**
 * Types 1 and 6 of the collisions are definitely inelastic because the cars don't move / bounce off each other.**
 * Types 2, 4 and 5 are definitely elastic collisions because the cars bounce off of each other.**
 * The total momentum before a collision is equal to the total momentum after the collision - if no external forces act on the system.**
 * The momentum of the original cue ball and the momentum of the 15 other balls right after they are hit, are equal. The objects will just have new directions with new speeds.**

· Based on the law of conservation of momentum, how can the traffic-accident investigators use to "reconstruct" the accident? What does it mean to "conserve" momentum? · Explain at least 1 cause of experimental error. Be sure you describe a specific reason. **The cars we used did not roll on the track that well, along with the fact that the motion detector could have picked up different feeds because it was placed in different areas.** · How would you improve the results of this lab? (In other words, what would you change about the materials or procedure to eliminate or reduce the experimental error you describe above?) **I would make sure (somehow) that the push was the same every single time, along with getting better carts that move along the track steadily.**
 * Conclusion:**
 * The investigators need to know the mass and the momentum of the cars. From that informations they can find the masses and momentum that will occur after the collision. To conserve is to maintain, the vehicles maintain the same momentum before & after a collision, as one can see in the data results above.**

USE THE RUBRIC TO MAKE SURE YOU HAVE INCLUDED ALL REQUIREMENTS!